It is known to admix inorganic or organic filaments with concrete in order to increase the strength of the concrete. Usually, these filaments do not disperse sufficiently uniformly and in particular build up procupine-like accumulations, the concrete after hardening does not have uniform strength. Also, the filaments can not have any desired thickness, since during the mixing operation very thin filaments do not maintain a longitudinal extension, but are mostly cropped together.
Hollow balls of polystyrene foam form light additives, which reduce the thermal conductivity of the concrete. This addition also reduces the strength of the concrete. The polystyrene balls float upwards easily during the mixing of the concrete, and may not be evenly distributed.